Gantry system and method for operating same

ABSTRACT

The invention relates to a gantry system for adjusting and aligning an ion beam onto a target from a freely determinable effective treatment angle. The ion beam therein is introduced in the horizontally arranged gantry rotation axis of the gantry system and is firstly deflected away from the gantry rotation axis by means of magnetic optics. The ion beam is then so aligned onto a target at adjustable angles of from 0 to 360° around the gantry rotation axis that the ion beam intersects the gantry rotation axis in the isocentre of the gantry system. Besides the gantry, the gantry system has a target carrier system having a rotatable target carrier, the carrier rotation axis of which is arranged in the isocentre in a vertical direction with the respect to the gantry rotation axis. The final deflection magnet so deflects the ion beam that the ion beam intersects the gantry rotation axis in the isocentre at an angle of between greater than or equal to 45° and less than 90°. Consequently, the ion beam can describe the surface of a cone when the gantry is rotated a full revolution about the gantry rotation axis. The target carrier system has a target carrier for each of two positions, which are perpendicular to one another in a vertical plane, it being possible to bring the carrier rotation axis into the isocentre of the gantry system. Furthermore, the invention relates to a method for irradiating a tumour from freely determinable effective treatment angles by means of the gantry system described above.

The invention relates to a gantry system for adjusting and aligning anion beam onto a target, according to the preamble of claim 1.

A gantry system of that kind is known from U.S. Pat. No. 4,870,287. Inthe case of the known gantry system, the ion beam is supplied to thegantry system in the horizontally arranged gantry rotation axis and isfirstly deflected from the gantry rotation axis by means of magneticoptics.

The ion beam is then guided parallel to the gantry rotation axis bymeans of magnetic optics and, from that direction parallel to the gantryrotation axis, is finally deflected into a radial direction with respectto the gantry rotation axis. The target is generally arranged at thepoint of intersection of the radially directed ion beam with the gantryrotation axis. That point of intersection is defined as the isocentre.

Consequently, on one full revolution of the gantry about the gantryrotation axis, the ion beam can be aligned onto the target in a planeperpendicular to the gantry rotation axis and adjusted to angles between0 and 3600°.

Besides the gantry, the gantry system comprises a target carrier systemhaving a rotatable target carrier. The carrier rotation axis of thetarget carrier is arranged in the isocentre in a vertical direction withrespect to the gantry rotation axis. Consequently, the gantry system,which comprises at least one gantry and one target carrier system, canso adjust and align an ion beam that a target arranged in the isocentrecan be irradiated from a freely determinable angle in space. In the of agantry system of that kind, it is necessary for the final deflectionmagnet of the gantry to deflect the ion beam by 90°, which is why agantry of that kind is also referred to as a 90° gantry.

In the case of the 90° gantry known from the publication U.S. Pat. No.4,870,287, therefore, the ion beam is, on leaving the gantry in thedirection of the gantry rotation axis, perpendicular to the gantryrotation axis. An angle α of gantry rotation is defined between theplane in which the ion beam is guided through the gantry and thehorizontal plane of the space in which the gantry rotation axis islocated. A horizontal position of the gantry accordingly corresponds toeither the angle α=0 or the angle α=180° when the gantry is in thehorizontal plane and consequently the ion beam is guided in the gantryin that horizontal plane. The uppermost position of the gantry in thevertical direction accordingly corresponds to the angle α=90° and thelowest position of the gantry has an angle of α=270°.

A treatment angle γ is defined between the horizontal plane of the spaceand the direction in which the ion beam enters a target volume. Aneffective treatment angle is defined between a frontal plane of apatient and the direction in which the ion beam enters a target volume.For a patient in a lying position, which is usual, the treatment angleand the effective treatment angle are identical.

In the 90° gantry system known from the publication U.S. Pat. No.4,870,287, the target carrier is in the form of a table rotatable abouta vertical axis and having a longitudinal axis and a transverse axis. Anangle β of target carrier rotation is defined between the longitudinalaxis of the target carrier table and the gantry rotation axis. By virtueof the rotatability of the target carrier about a vertical axis, theangle β can have values between 0° and 360°. For a prespecifiedtreatment angle γ, which is dependent upon the gantry rotation angle α,it is furthermore possible for a specific entry channel for tumourirradiation to be selected by adjusting the angle , of carrier rotation.By virtue of the adjustability of the angle β, which is associated withthe target carrier rotation, and the adjustability of the angle α, whichis associated with the gantry rotation, it is possible in a conventionalsystem, wherein the ion beam is deflected by the final deflection magnetin a radial direction with respect to the gantry rotation axis, for thetarget volume fixed on the target carrier to be aligned for any entrychannel for the purpose of tumour treatment.

The 90° gantry system known from the publication U.S. Pat. No. 4,870,287has the disadvantage that the final deflection magnet of the gantry mustdeflect the ion beam through at least 90° in order to make possible alltreatment angles β in a gantry system having a target carrier system.The large deflection angle of the final deflection magnet necessitates,depending upon the mass number of the ions to be deflected, a largeradius or a high magnetic field strength. Associated with that is thedisadvantage that, on the one hand, a gantry has hitherto beensuccessfully constructed only for ions having the smallest mass number,that is to say for protons; for ions having a higher mass number ofbetween 4 and 16 the final deflection magnet inflates the scale and massof the gantry to such an extent, because of the heavy ions having a massnumber higher than a proton, that a gantry system is no longerappropriate for clinical use.

In order to reduce the mass and volume of a gantry for ions that areheavier than protons, proposals exist for the use of super-conductingmaterials for the exciting coils of the deflection magnets. Although themasses to be rotated and the volume of the gantry would be reduced as aresult, the costs for cooling the super-conducting materials would makethe gantry system considerably more expensive, especially as 360°rotation is extremely problematic for a cooling system using liquidhelium or liquid nitrogen for modern super-conducting materials.

A further proposal, presented in the Japanese publication Journal of theJapanese Society for Therapeutic Radiology and Oncology, vol. 9, suppl.2, November 1997 as part of the Proceedings of the XXVII PTCOG Meetingby M. Pavlovic under the title “GSI Studies of a Gantry for Heavy IonCancer Therapy”, enables the mass and volume of the gantry to be reducedby changing the degree of deflection of the final deflection magnetfrom, formerly, 90° to 60°. That solution has the disadvantage that itis possible to achieve a treatment angle γ of only from 0° to 60° bymeans of a so-called 60° gantry of that kind in conjunction with theconventional target carrier system. Consequently, it is no longerpossible to achieve treatment angles γ of between greater than 60° and90° by means of a gantry system of that kind, which has a deflectionangle of 60° for the final deflection magnet.

The problem of the invention is to provide, by means of a gantry havinga reduced deflection angle of the final deflection magnet, a gantrysystem according to the preamble of claim 1 that does not requiresuper-conducting materials for the magnetic optics and that, despitereducing the deflection angle of the final deflection magnet to below90°, allows an ion beam to be adjusted and aligned onto a target from afreely determinable effective treatment angle. The problem of theinvention is furthermore to provide a method for irradiating a targetvolume and adjusting and aligning an ion beam for treatment of a tumourusing the gantry system according to the invention.

That problem is solved by the features of the subject matter of claims 1and 60.

For that purpose, the final deflection magnet so deflects the ion beamthat it intersects the gantry rotation axis in the isocentre at an angleof between greater than or equal to 45° and less than 90°, so that theion beam describes a surface of a cone on rotation of the gantry througha full revolution about the gantry rotation axis, and the target carriersystem has a target carrier for two positions, which are perpendicularto one another in a vertical plane, the carrier rotation axis of whichtarget carrier can be brought into the isocentre of the gantry system.Such a solution has the advantage that the target carrier has to befixable only in two specific positions and, in both positions, which areperpendicular to one another in a vertical plane, has to be rotatableabout a vertically aligned carrier rotation axis. A significantadvantage of this gantry system is that even angles that are less than90° and preferably less than 60° and that therefore advantageously makepossible an extremely low gantry volume and extremely small dimensionsfor the diameter of a gantry can be achieved by means of the gantrysystem according to the invention. Such a compact gantry system does notrequire expensive auxiliary equipment for cooling super-conductingmaterials. A further advantage of such a gantry having conventionalmagnetic optics is that it is now also possible for ion beams of ionsthat are heavier than protons, having mass numbers of between 4 and 16,to be adjusted and aligned for any freely determinable effectivetreatment angle by means of a gantry system that is suitable forclinical conditions.

In order to irradiate a target volume with an optimum dose distribution,there is preferably provided, in the case of the gantry system accordingto the invention, a deflection means for the ion beam in order to scanthe target volume layer by layer therewith. The ion beam is preferablyguided in the gantry, from the coupling-in point of the ion beam intothe gantry rotation axis to the deflection of the ion beam in the finaldeflection magnet of the gantry system, by first deflecting the ion beamaway from the gantry rotation axis using a 38° deflection magnet and bybringing it into a direction parallel to the gantry rotation axis usinga second 38° deflection magnet. In that parallel direction, the ion beampasses through two scanner magnets, which deflect the ion beam in twodirections oriented perpendicular to one another (horizontal andvertical with respect to the ion beam) and orthogonal to the ion beam,so that scanning of a surface of the target volume is advantageouslymade possible after the scan-deflected ion beam has passed through thefinal deflection magnet.

The preferred positioning of the scanning system upstream of the finaldeflection magnet accordingly reduces the gantry radius considerably andrequires, however, an enlarged aperture in order to allow a largetreatment area. That preferred arrangement of deflection magnet andscanning systems exhibits a high degree of ion-optical flexibility. Theion beam in the isocentre can therefore be modified advantageously from2 to 16 mm diameter and the magnetic optics of the gantry are alwaysachromatic.

In a preferred embodiment of the invention, the final deflection magnetso deflects the ion beam that the gantry rotation axis is intersected inthe isocentre at an angle of greater than or equal to 45° and less than60°. The deflection angles of below 60° especially show the enormousadvantages of the present invention in that, on the one hand, the gantrydimensions are minimised and, on the other hand, the gantry system inthe combination of the preferred embodiment of the gantry with thetarget carrier system according to the invention ensures that an ionbeam can be adjusted and aligned onto a target from a freelydeterminable effective treatment angle.

In a preferred embodiment of the invention, the target carrier systemhas a revolving platform, which is rotatable about a vertical revolvingplatform axis. Arranged on that revolving platform are two targetcarriers in two positions, the positions being perpendicular to oneanother in a vertical plane. Each of the two target carriers isrotatable about a vertical carrier rotation axis.

That preferred target carrier system allows for a patient to be arrangedin either a lying or a sitting position on the target carrier, dependingupon the effective treatment angle. For medical reasons, the effectivetreatment angle must be a freely determinable angle in the patientco-ordinate system in order to ensure as far as possible optimumscanning of the target volume by the ion beam.

Optimisation of the ion beam dose distribution in the target volume orin a volume element of the target is substantially dependent upon thestructure of the healthy tissue on top of the tumour volume, throughwhich healthy tissue radiation has to pass. The medical determination ofthe effective treatment angle and entry channel accordingly has to takeappropriate account of tissue cavities and densifications of tissue, forexample in the case of bone tissue, as well as the location of criticalorgans in the vicinity of the tumour. In that regard, a freelydeterminable effective treatment angle, which is made possible by thegantry system according to the invention, is a great advantage forclinical treatment.

The vertical carrier rotation axes of the two positions of the targetcarriers can preferably be brought alternately into the isocentre of thegantry system by means of a revolving platform as a result of rotationof the revolving platform about its revolving platform axis. Thispreferred embodiment is associated with the advantage that the patientcan be positioned in one of the two positions on the appropriate targetcarrier and can then be brought on the target carrier into the isocentreof the gantry system by means of the revolving platform. The gantry canthen be adjusted to the previously determined angle a and the targetcarrier in the selected position can be adjusted to the predeterminedangle β by means of a rotary movement about the vertical carrierrotation axis. After those three adjustments, the target volume can thenbe scanned with the scan-deflected ion beam.

In a further preferred embodiment of the invention, the target carriersystem has two separate delivery rails, on each of which there isarranged one target carrier of the two positions, the delivery railsbeing capable of laterally displacing, from different directions in eachcase, either of the target carriers with its rotation axis into theisocentre alternately. That system has the advantage that the patientcan be positioned and prepared on the selected target carrier outsidethe isocentre and can then be brought into the isocentre by displacementon the delivery rails. In the isocentre, the target volume can bescanned if in the meantime the gantry rotation angle α has been adjustedby rotation of the gantry and β has been adjusted by rotation of thetarget carrier.

In another preferred embodiment, the target carrier system has auniversal robot system, which arranges the target carrier in twopositions and arranges the vertical carrier rotation axes in theisocentre. Such multi-axis robot systems enable a rotatable targetcarrier to be arranged in different positions in the isocentre andconsequently replace the two target carriers of disparate constructionthat are otherwise necessary as well as any delivery rails or revolvingplatforms. Such a universal robot system can, for this preferredapplication, be greatly simplified, especially because only twopositions located perpendicular to one another in the vertical plane arerequired for the rotatable target carrier.

The method for irradiating a tumour from a freely determinable effectivetreatment angle by means of a gantry system is characterised by thefollowing method steps:

a) determining the most advantageous effective treatment angle and themost advantageous entry channel with respect to the location and size ofa tumour in healthy tissue and with the requirement for minimum exposureof the surrounding tissue to radiation together with optimumdistribution of an ion beam dose for the tumour tissue to be irradiated,

b) selecting, from two positions located perpendicular to one another ina vertical plane, the target carrier position required for thedetermined effective treatment angle,

c) bringing the carrier rotation axis of the suitable target carrierposition into the isocentre of the gantry system,

d) aligning and adjusting the target carrier by rotation of the targetcarrier about its vertical carrier rotation axis in respect of the mostadvantageous angle,

e) aligning and adjusting the gantry by rotation of the gantry about itshorizontal gantry rotation axis in respect of the most advantageousangle,

f) spatially scanning the entire tumour volume, by means of the ionbeam, from the effective treatment angle.

This method has the advantage that, by means of the combination of agantry system that is limited to treatment angles γ and a target carriersystem that delivers the target to the gantry isocentre in two positionslocated perpendicular to one another in a vertical plane, any freelydeterminable effective treatment angle can be adjusted for irradiatingthe tumour volume so that a target can be irradiated with ions withoutrestricting the effective treatment angle. In this context it isimmaterial whether the angle α is first adjusted by means of the gantryand then the angle β is adjusted by means of the target carrier orwhether the reverse order is selected.

It is merely of significance that for effective treatment angles of from0 to 90° minus λ only one position and therefore, preferably, one of thetarget carriers can be used and for angles between 90° minus λ and thedeflection angle λ of the final deflection magnet both positions of thetarget carrier can be utilised and for effective treatment anglesbetween the deflection angle of the final deflection magnet and 90° theother of the two positions for the target carrier can be employed. Thefundamental advantage of this method is consequently that, despite thefinal deflection magnet having a restricted deflection angle, the tumourto be treated can be treated with an ion beam from any freelydeterminable direction and therefore the medically optimal irradiationdirection can be achieved by means of a gantry system of reduced mass,volume and cost.

Further advantages, features and possibilities for use of the inventionare illustrated below using exemplary embodiments with reference to theannexed drawings.

FIG. 1 is a perspective view of an embodiment of the gantry systemaccording to the invention;

FIG. 2 shows a comparison between the action of the final deflectionmagnet of a conventional gantry and that of a gantry used in the gantrysystem according to the invention;

FIG. 3 shows the angular relationships and the definitions of angles fora gantry as they are used in the gantry system according to theinvention;

FIG. 4 shows the ion beam guidance of the gantry when α=90°;

FIG. 5 shows the ion beam guidance of the gantry when α=45°;

FIG. 6 is a side view of one of the two positions of the target carrier;

FIG. 7 is a side view of the other of the two positions of the targetcarrier;

FIG. 8 shows an arrangement of delivery rails according to a furtherembodiment of the invention.

FIG. 1 is a perspective view of an embodiment of the gantry system 6 ofthe invention. Such a gantry system 6 directs an ion beam 1 onto atarget 2. For that purpose, the ion beam 1 is supplied to the gantrysystem 6 in the horizontally arranged gantry rotation axis 4 and, bymeans of magnetic optics, is firstly deflected from the gantry rotationaxis 4 and then guided parallel to the rotation axis of the gantrysystem. The gantry 14 can perform a full revolution through anadjustable angle α of from 0 to 360°. During such a revolution the ionbeam describes the surface of a cone, the tip of which lies on thegantry rotation axis and intersects the gantry rotation axis in theisocentre 5. The gantry system 6 has a target carrier system 7 inaddition to the gantry 14. This target carrier system 7 has at least onerotatable target carrier 8, the axis of rotation 13 of which can bearranged in the isocentre in a vertical direction with respect to thegantry rotation axis 4.

The final deflection magnet 9 so deflects the ion beam 1 that itintersects the gantry rotation axis 4 in the isocentre 5 at an angle ofbetween greater than or equal to 45° and less than 90°. In theillustrated embodiment, that deflection angle is 55° so that the ionbeam 1 describes the surface of a cone having an angle of opening of110° when the gantry system 6 is rotated through a full revolution aboutthe rotation axis 4. In FIG. 1, the angle α has been adjusted to 90° sothat the ion beam deflection system of the gantry 14 is arranged in itsuppermost position. A target 2 arranged on the target carrier 8 in theposition 10 can be rotated about a vertical axis 13 in the isocentreand, despite the gantry having the possibility of complete revolutionfrom 0 to 360°, can be irradiated only up to treatment anglescorresponding to the exit angle of the ion beam from the magnetic opticsof the gantry. In the embodiment having a 55° gantry, that exit angle is55° with respect to a horizontal plane because the ion beam is deflectedonly by that 55° from a line parallel to the gantry rotation axis bymeans of the final deflection magnet 9.

With a target carrier 8 in position 10 it is therefore not possible toachieve all effective treatment angles. This preferred embodiment of theinvention therefore has a further target carrier 8 which makes possiblea second position 11 for the target, that position 11 being alignedperpendicular to position 10 in a vertical plane. In that position 11,the target can be acted upon at the effective treatment angles that arenot achievable in position 10, that is to say at effective treatmentangles of from 55° to 90°. Furthermore, effective treatment angles offrom 35 to 550 can be achieved with both positions 10 and 11 of thetarget carrier 8.

It is consequently possible, by means of this embodiment, to adjust anion beam and to align it onto a target, that ion beam hitting the targetfrom a freely determinable effective treatment angle despite the finaldeflection magnet 9 having a reduced deflection angle.

The entire target volume can be scanned volume element by volume elementand layer by layer by means of a scannable magnetic horizontaldeflection means 25 arranged upstream of the final deflection magnet 9and a scannable magnetic vertical deflection means 26 arranged betweenthe horizontal deflection means 25 and the final deflection magnet 9.That scanning is carried out layer by layer by means of the fact thatthe particular energy of the ion beam adjusts the depth of penetrationand, therefore, the height of the layer in the target.

As a result of appropriate programming of the horizontal deflectionmeans 25 and vertical deflection means 26, a very wide variety of targetvolume forms can be scanned and, as a result, tumour tissue can bedifferentiated from surrounding healthy tissue with razor sharpness.

By virtue of the increased mass moment of inertia of ions that areheavier than protons, a gantry system having an exit angle after thefinal deflection magnet of less than 90° has the advantage that thegantry system according to the invention can be constructed with asignificantly smaller radius than a conventional system which requiresdeflection of 90°.

This difference is clearly shown by a comparison in FIG. 2 illustratingthe action of a final deflection magnet of a conventional 90° gantry andthat of, for example, a 55° gantry used, for example, in a preferredembodiment of the gantry system.

In the prior art of a 90° gantry, which hitherto has been suitable onlyfor protons, the final deflection magnet deflects the ion beam 100 froma direction parallel to the gantry rotation axis 4 into a radialdirection with respect to the gantry rotation axis 4 and hits the targetat an adjustable angle α of between 0 and 360° according to the angle ofrotation of the gantry and, by rotating the target carrier 110, it ispossible to adjust almost any angle in space for irradiation of thetarget.

In this exemplary embodiment, with an exit angle from the finaldeflection magnet 9 at point E, the treatment angles γ are limited to 0°to 55°. In this case, compared to a 90° gantry, the isocentre 5 movesoutside the gantry from point I to point C, a considerable distance balong the gantry rotation axis 4, and at the same time the size of thefinal deflection magnet is considerably reduced so that either thevolume of the entire gantry can be reduced or the radius available forthe target carrier 8 and the patient to be treated can be increased by adistance l to a clear space of radius r. In fact, the space gained byreducing the deflection angle of the final deflection magnet 9 is usedfor reducing the overall size of the gantry system.

FIG. 3 shows in that regard the angular relationships and thedefinitions of angles for a gantry as they are used in the gantry systemaccording to the invention. In that regard the line 4 symbolises thegantry rotation axis, which together with the X axis fixes a horizontalplane. The ion beam, which emerges at point E, intersects the gantryrotation axis at point C, the isocentre 5.

FIG. 3 shows three positions of the gantry and the exit point E: firstlywhen the deflection system for the ion beam is in its uppermostposition, that is at E (90); then at a desired angle α at E (α); andfinally in a horizontal plane at E (0). Whereas the angle α can beadjusted by rotation of the gantry about its gantry rotation axis, theangle β is adjusted by rotation of the target carrier in a verticaldirection with respect to the gantry rotation axis, the carrier rotationaxis likewise passing through the isocentre 5 at point C.

The angle λ is prespecified by the final deflection magnet and remainsunchanged on all rotary movements of both the gantry rotation axis andthe carrier rotation axis. The treatment angle γ and the entry channelthrough which the beam penetrates into the patient are produced by thecombination of the two rotary movements, of the gantry and of the targetcarrier. The treatment angle γ is always less than or equal to λ and theeffective treatment angle is accordingly limited to one of the twopositions of the target carrier. If, however, the target carrieroccupies the second position, which is displaced through 90° in thevertical plane, the effective treatment angle for the target can beadjusted to the effective treatment angles in the first position. Thespacing d between the exit point E and the isocentre 5 at point Csimultaneously determines in conjunction with the angle λ describedabove the length a by which the isocentre projects out from the gantryand also the possible clear space of radius r that is available for theequipment for treating a patient in the gantry system according to theinvention.

FIG. 4 shows the guidance of the ion beam 1 of the gantry when α=90°,that is to say in the uppermost position of the deflection magnets. Thisgantry was designed for a 55° exit angle, the implementationspecifications having been so selected that an isocentric constructionis made possible and, at the same time, scanning of the target volume intwo active directions, that is to say layer by layer, is made possible,so that this embodiment essentially has the following advantageousproperties and arrangements:

1. achromatic beam optics,

2. modifiable beam size from 4 to 16 mm in steps of 1 mm,

3. a maximum beam energy of 400 MeV/u for a carbon ion beam having adepth of penetration into water of 27 cm,

4. a scanning field of size 20×10 cm²,

5. a scanning mode of low angular deviation, that is to say the anglebetween the impinging scanning beam and the perpendicular to the surfacebeing scanned is less than 1°,

6. a narrowing of the beam is located in the isocentre, that is to saythe narrowing of the beam in the isocentre has the advantage that thebeam circumference changes only very slightly in the vicinity of thenarrowing so that, as a consequence, variations in beam width can bedisregarded within a limited tumour volume, and finally

7. a minimum run from the gantry exit to the isocentre of 1.2 m.

A suitable arrangement of such a beam transport system having the aboveconstruction features is shown in FIG. 4. This gantry 14 consists of astraight adaptation region, in which the ion beam is introduced in thegantry rotation axis 4. That entry adaptation region consists of threequadrupoles 27 to 29. There is then a shoulder bend comprising two 38°deflection magnets 30 and 31 with two quadrupoles 32, 33 located betweenthem; an upper straight region, in which the ion beam is guided parallelto the gantry rotation axis 4, having three further quadrupoles 34 to 36and two scanning magnets with horizontal 25 and vertical 26 deflectionmeans for scanning the target volume; and a final 55° deflection magnethaving a large aperture.

The clear space for the patient has a radius of about 1.2 m, the outerradius of the gantry is about 2.8 m. Essentially, the size of the beamis advantageously determined mainly by the first three quadrupolesarranged in the curve-free region of the entry region. Such anarrangement exhibits a high degree of ion-optical flexibility. The beamin the isocentre can be of narrowed diameter from 2 to 16 mm and theoptics of the gantry always perform in an achromatic state.

FIG. 5 shows the same construction as FIG. 4 with the same componentsfor guidance of the ion beam at an angle α of 45°. In that respectidentical elements are referred to in FIG. 5 using identical referencesymbols.

FIG. 6 shows a side view of one of the two possible positions of thetarget carrier 8. The target carrier 8 is arranged in FIG. 6 in ahorizontal plane and can be rotated about a vertical axis 13. The targetcarrier carries a patient 40 having a tumour volume 20. The patient isarranged on the horizontal target carrier of a patient couch or apatient table so that the vertical carrier rotation axis 13 passesthrough the tumour volume 20, and the target carrier 8 is brought intothe isocentre 5 of the gantry system by means of the target carriersystem so that the tumour volume 20 is located in the isocentre 5.

FIG. 6 shows, as dotted areas, the regions that can be achieved aseffective treatment angles in a preferred embodiment of the invention bymeans of position 10 of the target carrier, whereas FIG. 7 shows thesecond position of the target carrier 8 and indicates, by means ofdotted areas, the further regions of a possible effective treatmentangle of an embodiment of the gantry system according to the invention.

FIGS. 6 and 7 clearly differentiate, in diagrammatic form, betweenhealthy tissue 22 through which radiation is to pass, unaffectedsurrounding tissue 23 and the tumour tissue 24 to be irradiated. Thedotted areas of FIGS. 6 and 7 are drawn for a deflection angle of 45°and clearly show that, even in the case of such a small deflection angleof the final deflection magnet as 45°, it is possible to adjust andalign an ion beam onto a target from freely determinable effectivetreatment angles.

FIG. 8 shows an arrangement of delivery rails 17, 18 and 19 according toa further embodiment of the invention. Opposite one another on the twodelivery rails 17 and 18 there are arranged a target carrier 8 in afirst position 10, wherein the target carrier is aligned horizontally,and a target carrier 8 in a further position 11, wherein the targetcarrier is aligned vertically. The target carriers can, in each case, berotated about their vertical axes 13.

After the most advantageous effective treatment angle for irradiating atumour volume has been determined, a patient can be arranged in arequired position 10 or 11 of the target carrier 8. The target carrier 8having the correct position 10 or 11 is then moved on one of the twodelivery rails 17 or 18, first up to a central delivery rail 19 and thenalong the delivery rail 19 towards the isocentre 5 of the gantry systemso that the carrier rotation axis of the suitable target carrier ispositioned in the isocentre of the gantry system.

Alignment and adjustment of the target carrier 8 by rotating the targetcarrier 8 about its carrier rotation axis 13 for the most advantageentry channel can be carried out before or after movement into theisocentre 5. Alignment and adjustment of the gantry by rotating thegantry about its horizontal gantry rotation axis for the mostadvantageous treatment angle can likewise be carried out before or aftermovement of the patient on the target carrier into the isocentre. Onlywhen adjustment of the suitable treatment angle and entry channel hasbeen completed by selecting the correct position of a target carrier 8and rotating the target carrier about its carrier rotation axis 13 aswell as by rotating the gantry about its horizontal gantry rotation axiscan spatial scanning of the entire tumour volume by the ion beam becarried out.

What is claimed is:
 1. A gantry system for adjusting and aligning an ionbeam (1) onto a target (2) from a freely determinable effectivetreatment angle, wherein the ion beam (1) is supplied to the gantrysystem (6) in the horizontally arranged gantry rotation axis (4) andfirstly is deflected away from the gantry rotation axis (4) by means ofmagnetic optics and then is arranged to be so aligned onto a target (2)at adjustable angles of from 0 to 360° around the gantry rotation axis(4) that the ion beam (1) intersects the gantry rotation axis (4) in theisocentre (5) of the gantry system (6), the gantry system (6) having agantry (14) and a target carrier system (7) which has a rotatable targetcarrier (8), the carrier rotation axis (13) of which is arranged in theisocentre in a vertical direction with respect to the gantry rotationaxis (4), wherein the final deflection magnet (9) so deflects the ionbeam (1) that it intersects the gantry rotation axis (4) in theisocentre (5) at an angle of between greater than or equal to 45° andless than 90°, so that the ion beam (1) describes a surface of a cone onrotation of the gantry (14) through a full revolution about the gantryrotation axis (4), wherein the carrier rotation axis (13) of the targetcarrier (8) can be brought onto the isocentre (5) of the gantry system(6), and wherein the target carrier system (7) has a revolving platform(15), which is rotatable about a vertical revolving platform axis (16),on which two target carriers (8) are arranged in two positions (10, 11),which are perpendicular to one another in a vertical plane, and each ofwhich is rotatable about a vertical carrier rotation axis (13). 2.Gantry system according to claim 1, characterised in that the finaldeflection magnet (9) so deflects the ion beam (1) that the ion beam (1)intersects the gantry rotation axis (4) at an angle greater than orequal to 45° and less than 90°.
 3. Gantry system according to claim 1,characterized in that the vertical carrier rotation axes (13) of the twopositions (10, 11) of the target carriers (8) are arranged to be broughtalternately into the isocentre (5) of the gantry system (6) by means ofa revolving platform (15) as a result of rotation about a revolvingplatform axis (16).
 4. A gantry system for adjusting and aligning an ionbeam (1) onto a target (2) from a freely determinable effectivetreatment angle, wherein the ion beam (1) is supplied to the gantrysystem (6) in the horizontally arranged gantry rotation axis (4) andfirstly is deflected away from the gantry rotation axis (4) by means ofmagnetic optics and then is arranged to be so aligned onto a target (2)at adjustable angles of from 0 to 360° around the gantry rotation axis(4) that the ion beam (1) intersects the gantry rotation axis (4) in theisocentre (5) of the gantry system (6), the gantry system (6) having aganry (14) and a target carrier system (7) which has a rotatable targetcarrier (8), the carrier rotation axis (13) of which is arranged in theisocentre in a vertical direction with respect to the gantry rotationaxis (4), wherein the final deflection magnet (9) so deflects the ionbeam (1) that it intersects the gantry rotation axis (4) in theisocentre (5) at an angle of between greater than or equal to 45° andless than 90°, so that the ion beam (1) describes a surface of a cone onrotation of the gantry (14) through a full revolution about the gantryrotation axis (4), and the target carrier system (7) has two positions(10, 11) for a target carrier (8), which positions are perpendicular toone another in a vertical plan wherein the carrier rotation axis (13) ofthe target carrier (8) can be brought into the isocentre (5) of thegantry system (6), and wherein the target carrier system (7) has twoseparate delivery rails (17, 18), on each of which there is arranged onetarget carrier (8) of the two positions (10, 11), the delivery rails(17, 18) being capable of laterally displacing, from differentdirections in each case, either of the target carrires (8) with itscarrier rotation axis (13) into the isocentre (5) alternately.
 5. Agantry system for adjusting and aligning an ion beam (1) onto a target(2) from a freely determinable effective treatment angle, wherein theion beam (1) is supplied to the gantry system (6) in the horizontallyarranged gantry rotation axis (4) and firstly is deflected away from thegantry rotation axis (4) by means of magnetic optics and then isarranged to be so aligned onto a target (2) at adjustable angles of from0 to 360° around the gantry rotation axis (4) that the ion beam (1)intersects the gantry rotation axis (4) in the isocentre (5) of thegantry system (6), the gantry system (6) having a gantry (14) and atarget carrier system (7) which has a rotatable target carrier (8), thecarrier rotation axis (13) of which is arranged in the isocentre in avertical direction with respect to the gantry rotation axis (4), whereinthe final deflection magnet (9) so deflects the ion beam (1) that itintersects the gantry rotation axis (4) in the isocentre (5) at an angleof between greater than or equal to 45° and less than 90°, so that theion beam (1) describes a surface of a cone on rotation of the gantry(14) through a full revolution about the gantry rotation axis (4), andthe target carrier system (7) has two positions (10, 11) for a targetcarrier (8), which positions are perpendicular to one another in avertical plane, wherein the carrier rotation axis (13) of the targetcarrier (8) can be brought into the isocentre (5) of the gantry system(6), and wherein the carrier system (7) has a universal robot system(19), which arranges the target carrier (8) in the two positions (10,11) and arranges the vertical carrier rotation axis (13) in theisocentre (5).
 6. Method for irradiating a tumour from freelydeterminable effective treatment angles by means of a gantry system (6)according to claim 1, characterized by the following method steps:determining the most advantageous effective treatment angle and the mostadvantageous entry channel with respect to the location and size of atumour (21) in healthy tissue (22) and with the requirement for minimumexposure of the surrounding tissue (23) to radiation and optimumdistribution of an ion beam dose for the tumour tissue (24) to beirradiated, selecting, from two target carrier positions (10, 11)located perpendicular to one another in a vertical plane, the targetcarrier (8) position required for the determined effective treatmentangle, bringing the carrier rotation axis (13) of the selected position(10, 11) of the target carrier (8) into the isocentre (5) of the gantrysystem (6), aligning and adjusting the target carrier (8) by rotation ofthe target carrier (8) about its vertical carrier rotation axis (13) inrespect of the most advantageous entry angle, aligning and adjusting thegantry (14) by rotation of the gantry (14) about its horizontal gantryrotation axis (4) in respect of the most advantageous treatment angle,spatially scanning the entire tumour volume (20), by means of the ionbeam (1), from the treatment angle adjusted for the ion beam (1) andthrough the entry channel adjusted.